1. Field of the Invention
The present invention relates to a printer apparatus for forming a raised image, that is, a so-called embossed image, on a print supporting member, such as a paper sheet.
2. Description of the Related Art
Emboss printing is widely used to make printed matters impressive. For example, firm's names and trademarks are often embossed on business cards, letter papers and envelopes. Also, many invitation cards, Christmas cards, birthday cards or the like are embossed with greeting words and other decorative images.
Further, emboss printing is used to produce braille, embossed graphs or the like in publications for visually handicapped people to read by touching.
Various methods of forming embossed images have been invented and used.
FIG. 8 shows a first method of forming an embossed image. In this method, a print supporting member 81, such as printing paper, is pressed between a male die 82 and a female die 83 which have a raised pattern and a recessed pattern, respectively, of characters, graphics, braille or the like. The print supporting member 81 is thus embossed with the characters, graphics, braille or the like.
FIG. 9 shows a second method of forming an embossed image. In this method, characters, graphics, braille or the like are printed on a print supporting member 91, such as printing paper, in a highly-adhesive ink 92 by using an ordinary printer such as a screen printer or an offset printer, thus producing an initial image pattern. Then, thermoplastic resin powder 93 is dusted over the print supporting member 91. The thermoplastic resin powder 93 adheres to the initial image pattern formed of the highly-adhesive ink 92. After removing the thermoplastic resin powder 93 lying on portions other than the initial image pattern, heat is applied in order to dry the ink 92 and melt and completely fix the remaining thermoplastic resin powder 93, thus forming an embossed image of the characters, graphics, braille or the like.
FIG. 10 shows a third method of forming an embossed image. Using a copying machine or the like, an initial image pattern is formed of a highly heat-absorptive black toner 102 on a foamable paper sheet 100 which contains foamable micro-capsules 101. Then, the foamable paper sheet 100 carrying the initial image pattern is heated by using, e.g., infrared rays. As the temperature of the black toner 102 rises, the adjacent foamable micro-capsules 101 produce bubbles 103, thus expanding the toner-adjacent portions of the paper sheet 100 to form an embossed image.
FIG. 11 shows a fourth method of forming an embossed image, in which a braille embossing printer is used. As shown in the figure, printing paper 111 is placed between a metallic plate 114 having small hemispherical recesses and electromagnetic solenoids 113 having small circular metallic tips 112. By supplying current to the electromagnetic solenoids 113, the small circular metallic tips 112 are moved to strike the printing paper 111 against the small recesses of the metallic plate 114, thus embossing braille points.
The above-described known methods of forming embossed images have problems as follows.
Though the above-described first method is suitable to produce large amounts of high-quality emboss-printed items, it takes a very precise milling machine and a long processing time to precisely form the male and female press-dies, that is, printing original plates, respectively having the raised and recessed patterns of an image. Thus, the production cost of the press dies is substantially high. Further, because the press dies must be pressed onto the print supporting member by a great pressure, a large pressing machine is required. Since most large pressing machines produce great noises and vibrations, means for mitigating such noises and vibrations must be provided.
The above-described second method also has a problem in that formation of a printing original plate requires a substantially long time and high cost, though a printing original plate according to this method is easier to obtain than the printing original plates according to the first method. Further, this method needs a large printer for forming an initial image pattern on a print supporting member by using a printing original plate and a large apparatus for applying thermoplastic resin powder to a print supporting member and heating the print supporting member so as to melt the thermoplastic powder applied thereto. Because these apparatuses take up much space and produce loud noises, this method is not very suitable to perform in offices or homes. Still further, the thermoplastic resin powder mostly form monoparticle layers on the adhesive ink, as shown in FIG. 9, because the powder particles are fixed to the ink by the adhesiveness of the ink. Therefore, it is difficult to obtain a polyoparticle layer, which means that this method is unsuitable to form an embossed image having a great height.
The above-mentioned third method can be suitably performed in offices and homes because the printing apparatus used in this method is relatively small and quiet. However, because production of the foamable paper containing foamable microcapsules requires a specifically constructed apparatus, the production cost of the foamable paper is nearly three digits greater than the production cost of copying paper. Further, because the height of an embossed image achieved by formation of bubbles in the paper is at most half the thickness of the paper, the paper must be substantially thick in order to obtain a sufficiently high embossed image. Still further, because the images are embossed by bubbles formed in the paper, the embossed images fail to obtain a substantial strength to resist forces imposed on their top surfaces, thus causing problems in storability and durability.
In the above-described fourth method, a paper sheet is pressed between the small recesses of the metallic plate and the small circular metallic tips which are moved to strike the plate by the force created by the electromagnetic solenoids, as described above. Thus, embossed images are formed by stretching or breaking the fibers of the paper. Because it takes a great force to stretch or break the paper fibers, the electromagnetic solenoids must create great forces so that the metallic tips strike the paper sheet against the metallic plate sufficiently hard, thus causing noises having high-frequency components, which are typical of noises produced by metal impacting on metal. Therefore, though the braille embossing printer according to this method is relatively small, it is not very suitable to use in offices or homes.
Further, electric typewriters are widely used for emboss printing. One cycle of striking and returning of the electromagnetic solenoid of an electric typewriter produces either one character or one braille point. Therefore, it takes six or eight of such cycles to produce one braille character because one braille character is a combination of six or eight braille points. Further, a substantial distance must be provided between braille points because, otherwise, formation of one braille point would result in deformation of the adjacent braille points. Therefore, electric typewriters are not suitable for either high-speed emboss printing or formation of a continuously embossed line or a minute graphic.
There is a growing demand for an emboss printing apparatus which is able to perform high-speed emboss printing and produce emboss-printed items of many different types but not necessarily in large amounts and which is small and quiet and inexpensive to operate and, therefore, is suitable to use in offices and homes, just as is desired for an ordinary-type printing apparatus.